To deal with the exponential growth in mobile data demand, mobile (cellular) network operators are using two different approaches. One aspect is the densification of the networks, resulting in large scale deployments of small cells. The other is the utilization of more spectrum, be it in a multiple Radio Access Technology (multi-RAT) format or as carrier aggregation or wider bandwidths. The multiple RATs include 4G LTE and, importantly, wireless local area networks (WLAN, but often known as WiFiTM) for the small cells. It is expected that, in the near future, there will be a very large scale deployment of dual mode (e.g. Long Term Evolution—LTE—and WiFi) supported femto base stations/femtocells (small, low-power cellular base stations) in public spaces like shopping malls, railway stations and airports. It will be cost effective for operators to collaborate and deploy multi-operator femtocells in these public spaces. There may even emerge third party entities to install and maintain these femtocells, leasing capacity to the operators.
The main problem in achieving a multi-operator, dual mode femtocell will be the number of operations carriers it has to support. In particular, the LTE spectrum is highly fragmented and with each operator having two to three LTE carriers, a default multi-operator femtocell would have to support about ten to twelve LTE carriers. This would push up the cost, size and complexity of the femtocells. Furthermore, LTE carriers are not harmonized globally and it would be difficult to support roaming users in some situations. There are many femto networks, for example in airports, hotels or department stores, where roaming users make up a significant percentage of the user population. In many cases, especially with users visiting from abroad, the fragmented LTE bands do not overlap sufficiently. From an operator perspective, supporting roaming users is critical, as this brings in significant revenues. In some cases the operators would have to deploy different femtocells to support both local users and roaming users and this would be highly ineffective in terms of cost and complexity.
It is desirable to facilitate the use of dual mode femtocells.